Project Summary Our research program aims to define the systems that support number symbol learning during early childhood ? a foundational issue in the fields of cognitive development and cognitive neuroscience. The question of how number word acquisition unfolds in the developing brain is an untested phenomenon. By using fMRI in longitudinal studies of 3- to 7-year-old children, we will assess, for the first time, how neural representations of numerical concepts change as children develop capacity with spoken number words and numerals and how patterns of cortical activation relate to children?s mathematical competence in school. Current evidence from adults and older children suggests that number words are not processed by the brain as typical words, in semantic regions of temporal cortex, but are instead grounded in the perceptual mechanisms of parietal cortex that represent spatial and quantitative dimensions. Based on previous research and our preliminary data, we hypothesize that the intraparietal sulcus (IPS) grounds the development of symbolic number representations in perceptual representations of quantity. We will test the degree to which perceptual representations of quantity in parietal cortex exhibit functional overlap with symbolic number representations during early childhood. Our research brings new theoretical distinctions, innovative methods, and new types of data to a long-standing behavioral research tradition on the development of number words. The hypotheses, experiments, and analyses that we propose are all well- founded in prior research but also offer novel insights with broad significance for mathematical cognition, education, and language development. These basic research advances will provide foundational knoweldge for research on learning impairments.